 
(* ::Section:: *)
(* PauliIndexDelta *)
(* ::Text:: *)
(*PauliIndexDelta[PauliIndex[i], PauliIndex[j]] is the Kronecker-delta in the Pauli space with two explicit Pauli indices i and j..*)


(* ::Subsection:: *)
(* See also *)
(* ::Text:: *)
(*PauliChain, PCHN, PauliIndex, DIDelta, PauliChainJoin, PauliChainCombine, PauliChainExpand, PauliChainFactor.*)



(* ::Subsection:: *)
(* Examples *)



PauliIndexDelta[PauliIndex[i],PauliIndex[j]]

PauliIndexDelta[PauliIndex[i],PauliIndex[j]]^2

PauliChainJoin[%]

PauliChainJoin[%%,TraceOfOne->D]

PauliIndexDelta[PauliIndex[i],PauliIndex[j]]PauliIndexDelta[PauliIndex[j],PauliIndex[k]]

PauliChainJoin[%]

PauliChain[PauliEta[-I],PauliIndex[i0]]PIDelta[i0,i1]//FCI//PauliChainJoin

PauliIndexDelta[PauliIndex[i2],PauliIndex[i3]] PauliIndexDelta[PauliIndex[i4],PauliIndex[i5]] PauliChain[PauliIndex[i7],PauliXi[I]] PauliChain[PauliEta[-I],PauliIndex[i0]] PauliChain[PauliSigma[CartesianIndex[a]],PauliIndex[i1],PauliIndex[i2]] PauliChain[PauliSigma[CartesianIndex[b]],PauliIndex[i5],PauliIndex[i6]] PauliChain[m+PauliSigma[CartesianMomentum[p]],PauliIndex[i3],PauliIndex[i4]]

PauliChainJoin[%]

PauliChainJoin[% PIDelta[i0,i1]]

PauliChainJoin[% PIDelta[i7,i6]]
